El Niño/Southern Oscillation (ENSO)

The conditions in the tropical Pacific remain neutral (neither El Niño nor La Niña). All atmospheric and oceanic indicators are in the neutral range.

Between January and February 2013, the cold anomalies that were present in the eastern equatorial Pacific have weakened, while the region of colder than normal SSTs in the southeast Pacific has extended westward. SSTs around Australia are currently much warmer than normal (reaching more than +1°C).

February NINO values are –0.33°C for NINO3.4 (down from –0.2°C in January 2013), –0.06°C for NINO3 (up from –0.3°C in January 2013) and –0.09°C for NINO4 (was +0.2°C in January 2013).

Warmer than normal subsurface temperatures still exist along the Equator at about 150m depth west of the Dateline, while cooler than normal temperatures are present east of the Dateline, but the amplitude of the anomalies has diminished in the past couple of weeks.

The trade winds are currently slightly stronger than normal in the central and west Pacific, but close to climatological values elsewhere. Convection in February was intensified along and north of the Equator, to the west of the Dateline, and the South Pacific Convergence Zone was not very coherent spatially.

The latest value for the TRMM ENSO index for the 30 days to March 3rd is –0.91 (on La Niña side of neutral) and the monthly SOI for February is –0.5.

An active Madden – Julian Oscillation moved into Australian longitudes over the last two weeks of February and is forecast to slowly move eastward over the coming two weeks.

All the climate models that NIWA monitors are in agreement and indicate that neutral ENSO conditions are very likely to persist over the coming 3 months (March - May 2013), with sea surface temperatures along the equator close to climatological values. 

Surface temperature anomalies (ºC) for February 2013, data is from the NOAA OISST Version 2 dataset, available at the NOAA’s Climate Data Center (ftp.cdc.noaa.gov/Datasets/noaa.oisst.v2.highres).